Charging 1 euro is practical (so they don't have to be giving out a ton of change during the day...), but it sounds like they should have made sure they were offering something that didn't look too cheap -- e.g., get decent quality plastic cups that aren't tiny, do some actual work for each customer (instead of just pouring from a massive pre-filled jug), include a lemon wedge in each cup, etc..

I can easily imagine a lemonade-stand lemonade that would seem underpriced at 1 euro; but obviously they didn't take that approach!